This invention relates to apparatus useful in performing analytical tests on liquid samples under pressure and more particularly to apparatus for supporting a filter membrane and intercepting filter effluent.
Apparatus for performing certain analytical tests on liquids, including the filter plugging or Silt Density Index (SDI) test for monitoring the particulate content of feed water to membrane water treatment processes such as reverse osmosis, typically includes a filter holder for supporting a filter membrane through which the pressurized test sample flows. Such apparatus typically requires connecting the filter holder to a sample outlet line as well as to the sample inlet line. When a fresh filter membrane is inserted into the apparatus of such a system, air tends to become entrained in the system. In such a system any air pockets or bubbles remaining after a purge will interfere with a subsequently performed analysis. In some apparatus the filter holder may not be connected to a sample outlet line, and filter effluent may be permitted to freely exit the filter holder outlet. In such a system the filter effluent may be merely discharged to a sink or similar drain, or it must be separately collected for alternate disposal. Discharging effluent to a drain tends to be messy because of uncontrolled splashing, while separately collecting the effluent is time consuming and inconvenient, particularly when many samples must be analyzed.
Further, in existing apparatus of the type described there is provision only for a single filter cartridge at a time, which requires manual replacement of the filter cartridge after each SDI test, as well as a shutdown of the testing apparatus while the spent filter cartridge is replaced.
Thus, there is still a need for apparatus for holding one or more filters which permits deflecting filter effluent, which is easy to purge of air or dispenses with the need to purge air after a filter change, and which permits an unattended sequence of SDI tests, and uninterrupted operation of SDI testing apparatus.